Filters are routinely used within conduits for filtration and their use in such applications is both well known and widespread. In most applications filters are designed to be securely seated against the forces of fluid flow. In connection with prior art directed to the provision of oral medications, it is known to use filters as a substrate to support medication within a conduit such as a drinking straw. Such devices typically contain a single dose of medication which, in some circumstances, is supported by either a screen or a porous material which is wedged between the sidewalls of the straw. Some devices may provide a separate support structure to maintain the screen or filter in place. The prior art also discloses the use of solid impediments which will move within a conduit in response to fluid flow in connection with other applications. Such solid impediments typically have a diameter less than the diameter of the conduit and thus are not designed to frictionally engage the conduit or to be retained in a stationary position. One application where such solid impediments are used is in connection with the regulation and or metering of fluid flow.
In connection with the provision of oral medications, straws are frequently used to administer a single dose of a drug. In such devices, fluid enters the straw, passes through the filter, then puts the drug into suspension or solution, and next exits the opposite end of the straw. It is desirable to provide a substrate which would support the drug and allow the patient to draw liquid through the straw and, enable the substrate to move a predetermined distance depending on the volume of fluid which passed through the straw. The movement of the substrate in the device in response to fluid flow would provide a visual indication as to whether a predetermined amount of fluid had passed through the straw and consequently was ingested by a patient. Accordingly, it is one object of the invention to provide a substrate which will both support medication within a straw, allow for the administration of the medication and further allow the substrate to move in response to the flow of fluid. It is a further object of the present invention to provide a material within a conduit which will remain seated within the conduit in response to fluctuations in air pressure, however move in response to fluid flow under conditions analogous to those created and typically encountered using a drinking straw. A further object of the invention is to provide a substrate which allows air to freely travel through an impediment and thus exhibit no response to air flow however, when liquid is allowed to contact the impediment, the impediment may move in response to the flow. A further object of the present invention is to provide a device which provides an indication of whether a predetermined amount of fluid has passed through a conduit. Yet a further object of the invention is to provide a device to assist in the oral delivery of solid medication which provides an indication of whether or not a predetermined amount of fluid has passed through the liquid and thereby provide an indication as to whether or not medication has been ingested. A further object of the invention is to provide a device which is appealing and which provides encouragement to children by providing a positive indication that a medication has passed through a conduit.